A communication network is a means for conveying information from one place to another. The information can be in audio, digital data, video, text, graphics, data, sign language or other forms. The network can be a wide area network such as an intranet in an office, store or factory. Establishing and maintaining communication networks is one of the oldest known activities of mankind ranging from the shouting and drum signals of prehistory through written messages, signal flags, signal fires, smoke signals, signal mirrors, heliographs, signal lanterns, telegraphs, radios, telephones, televisions, microwave signals, linked computers and the internet. Improving communication networks will continue to be a major technical focus in the future.
The ideal communication network would be non-intrusive, inexpensive, extremely large information carrying capability (wide bandwidth), instantaneous and suitable for use with a broad variety of transmission and reception technologies.
There have been a few reports of the use of visible lighting as a carrier in electronic communication networks. The earliest reference to using lighting to send electronic information as well as to provide illumination appears to be Dachs (U.S. Pat. No. 3,900,404) disclosing an analog amplitude-modulation (AM) scheme to modulate the arc current in a fluorescent lamp, the xe2x80x9ccarrierxe2x80x9d signal, with an audio information signal. King, Zawiski and Yokoun (U.S. Pat. No. 5,550,434) disclosed an updated electronic circuit that also provides for AM modulation of the arc current with an analog signal. Smith (U.S. Pat. No. 5,657,145) teaches a method for encoding low-bandwidth digital information into the lamp light using a pulsed AM technique. The encoding technique involves chopping 100 microsecond slices of current out of the arc waveform. Nakada ( Japanese Patent application 60-32443, Feb. 19, 1985.)reports a FM modulation and a frequency shift keying (FSK) scheme to transmit digital data using visible lighting. Gray (U.S. Pat. No. 5,635,915 Jun. 3, 1997 and PCT WO90/13067, Oct. 11, 1991.) has reported a product pricing system for supermarket shelf labels where a signal is sent from visible lighting to individual product price labels on shelves to cause the listed prices to change when desired.
Other communication schemes have been proposed that do not use the lamp light as the carrier, but instead use the lamp fixture as an antenna for transmitting conventional radio wave or microwave signals. In Uehara and Kagoshima (U.S. Pat. No. 5,424,859), for example, the inventors disclose techniques for mounting a microwave antenna on the glass surface of fluorescent and incandescent lamps. Buffaloe, Jackson, Leeb, Schlecht, and Leeb, ( xe2x80x9cFiat Lux: A Fluorescent Lamp Transceiver,xe2x80x9d Applied Power Electronics Conference, Atlanta, Ga. 1997) first outlined the possibility of using pulse-code modulation to transmit data with a fluorescent lamp. In the latter reference, a three-level code shifts the arc frequency to one of three possibilities every Tsw=2 milliseconds. The result is a steady light output, on average, with no perceptible flicker. A one or a zero bit does not correspond to a particular arc frequency, but rather, to a three level pattern in arc frequency. A logic zero bit is transmitted by varying the arc frequency first to 40 kHz, then to 38 kHz, and finally to 36 kHz. A logic one bit is transmitted by the arc frequency pattern beginning with 38 kHz, followed by 40 kHz, and ending with 36 kHz. A unique start bit, used to demarcate the beginning of a transmitted byte, is represented by a sequence in the arc frequency beginning with 36 kHz, followed by 38 kHz, and ending with 36 kHz.
In our previously filed patent applications Ser. No. 09/291,706 filed Apr. 14, 1999 and entitled xe2x80x9cDual-Use Electronic Transceiver Set for Wireless Data Networksxe2x80x9d and application Ser. No. 07/292,126 filed Apr. 14, 1999 entitled xe2x80x9cAnalog and Digital Electronic Receivers for Dual-Use Wireless Data Networksxe2x80x9d, we have disclosed visible light communications networks for analog and digital data based on frequency modulation of light. The modulation techniques include direct FM, 2 level half weight bit coding and other orthogonal bit coding schemes.
The visible light case mentioned above is a specific case of our invention which, stated generally, involves simultaneous intentional dual use of transmitted electromagnetic radiation for two completely different useful purposes.
With the new technology disclosed in our previously filed applications, the recent advances in computer technology and other improvements in electronics, a number of applications and uses are now enabled. These applications are most preferentially executed using our new technology. However, in some cases, they may be executed using some of the other technologies known in the prior art.
With reference to FIG. 4, our communication network contains the following elements in series:
a) A source (50) of the information which will be transmitted;
b) A transmitter (54), which includes lamp and a means for controlling the modulation of the lamp to cause the lamp to carry a signal;
c) A medium (56) through which the light passes from the transmitter to the receiver (60, 76 or 108);
d) A receiver for receiving and demodulating the light in order to obtain the information; and
e) A user (62, 96 or 98) for the information. This user can be a device, like a computer or a compact disk player, or it can be a person.
Our invention embodies a number of uses and purposes for the light based communication network. One purpose is to process the signal from the light is by the receiver to control the selection of information from a computer memory, CD or other storage device for large scale storage of data, greatly increasing the effective bandwidth of the information which can be transmitted. Another purpose is to provide data to the user from the receiver from both a large scale data storage device, like a computer memory, compact disk or other such device, and from the information transmitted by the light, with segments of data from the sources interspersed in presentation to the user. Another purpose is to provide data from a device source, like a computer chip, a tape cassette a compact disk or other such device, to the transmitter. Another purpose is to repeat continually the data from the device source, providing a continuous signal of finite period to the user. Another purpose is to use two or more transmitting lights, each transmitting its own signal at the same frequency to provide spatial resolution of signal so that the receiver will receive and provide to the user information from only one of the lights at any time and the receiver may shift its reception from one light to another. Another purpose is to transmit two or more different signals simultaneously at different frequencies from one light in such a manner that two or more receivers can each pick up the different signals. Another purpose is to transmit two or more different signals containing the same information in two or more different languages or codes so that by selecting the proper frequency, the user can select information in the language or code they deem most suitable. Another purpose is to encrypt the information prior to transmission and decrypted it subsequent to receipt. Another purpose is to use the lighting of an individual exhibit to provide to the user a description of some aspect of the exhibit. Another purpose is to transmit information over the network is used to provide assistance to individuals who are visually impaired. Another purpose is to transmit information transmitted over the network to provide assistance to individuals who are hearing impaired. Another purpose is to transmit over the network to provide assistance to individuals who are mentally impaired. Another purpose is to transmit the information transmitted over the network for processing by the user and subsequent sending out of a responding signal by the user using some means. Another purpose is to use the network to provide information to a receiver and user which are moving. Another purpose is to use the network to provide information inside an aircraft, boat, submarine, bus, auto, train or other vehicle. Another purpose is to use the network to provide guidance information to a receiver and user which are moving. Another purpose is to use the network to provide safety or warning information. Another purpose is to use create a network where the same information is being provided by a plurality of different lights. Another purpose is to use the network to provide paging information to the user. Another purpose is to provide information in classrooms and other meeting rooms. Another purpose is to create a repeater network where the modulated signal initiated by one light will be received by an adjoining light, that light started modulating, etc. until all lighting in a network is being modulated and carrying the signal. Another purpose is to create a network in which the electromagnetic radiation which is modulated is infrared radiation. Another purpose is to create a network in which the electromagnetic radiation which is modulated is ultraviolet radiation. Another purpose is to create a network in which the electromagnetic radiation which is modulated is radio frequency radiation. Another purpose is to create a network in which the electromagnetic radiation which is modulated is microwave radiation. Another purpose is to create a network in which the electromagnetic radiation which is modulated is X-ray radiation. Another purpose is to create a network to transmit compressed data.